Socket wrenches are used for screwing or unscrewing hexagonal screw members (such as screws or nuts). Due to a clamping push force applied by six sides or six corners, a solid and stable output effect can be achieved. The wrench may cooperate with a one-way ratchet gear mechanism to form a ratchet wrench having a turning function. However, the socket wrench is sleeved on the hexagonal screw member only in the axial direction. For hexagonal screw members of a pipe connector (such as nuts for pipe fitting), an open-end wrench is used to screw or unscrew the hexagonal screw members. The jaw of the open-end wrench is formed with a jaw opening for guiding a hexagonal screw member. Relative to the shape of the hexagonal screw member, at least a pair of sides of the hexagonal screw member cannot be applied with a force by the jaw of the wrench, which will affect the operation of the wrench. As a result, the hexagonal screw member cannot be screwed stably. The operation of the handle of the open-end wrench has a backswing limit of 360 degrees. The opening of the jaw needs to be in and out at two different sides of the hexagonal screw member, which affects the continuous operation for screwing the hexagonal screw member. A conventional quick open-end wrench based on the structure of a clamp is disclosed. The clamping space of the jaw can be changed to achieve the function of a backswing operation. However, its two clamping arms only act on three sides of a screw member. The wrench cannot screw the screw member stably. The mechanism for controlling the opening or closing of the jaw increases the complexity of the structure. The structure of the open-end wrench cannot be simplified. Another conventional ratchet wrench capable of operating continuously is disclosed. The ratchet wrench has a jaw opening formed by two clamping arms. The jaw opening is normally open so that two opposite sides of a hexagonal screw can be directly inserted into the jaw opening for performing a backswing operation. Although the ratchet wrench is able to clamp four sides of the hexagonal screw member, the open jaw opening may cause the hexagonal screw member to slide out of the jaw opening easily. During the process that the wrench is used to screw a hexagonal screw member, the hexagonal screw member may slide out of the jaw opening (affecting the stability of the operation). In the embodiment as shown in FIG. 13, an end of an extension sleeve 30 (movable arm) is bent to form an end surface 56 which acts on the fifth side of a hexagonal screw member to increase an output point or surface, thereby preventing the hexagonal screw member from sliding out of the jaw opening. But, this design affects or hinders the hexagonal screw member from entering the jaw opening. Accordingly, the inventor of the present invention has devoted himself based on his many years of practical experiences to solve these problems.